Cationic resins containing Mannich base groups are known. These are soluble in water with the aid of a solubilizing acid, even after post reaction with diepoxides. The known materials are described in U.S. Pat. Nos. 3,994,989 and 4,001,155. While these known materials have various deficiencies which are avoided by the prior contribution of two of us (K. Sekmakas and R. Shah in Ser. No. 160,606 Filed June 18, 1980) the corrosion resistance is still marginal, and improvement in this characteristic is the prime objective of this invention.
All of the efforts referred to in the preceding patent involve a bisphenol as the starting material. This is not done in this invention. Also, water solubility is obtainable in these prior efforts even when the water solutions are neutral or significantly alkaline. This is an advantage since it permits the formulation of electrocoating baths which are not significantly acidic, and hence not corrosive, and this advantage is retained herein. Moreover, in the prior contribution of Sekmakas and Shah referred to above, a superior distribution of Mannich base groups is obtained which leads to improved bath stability. This advantage is also retained in this invention where the distribution is again better than in the patents noted above.